1. Field of the Invention
The present invention relates to a capacitive touch panel and a display device using the capacitive touch panel.
2. Description of the Prior Art
Display panels and flat screen display device using display panels are becoming the mainstream in the field of display devices. For instance, flat television for home use, liquid crystal monitor of the personal computer or of the laptop, display screen of mobile phone and digital camera are products which incorporate the display panel as essential component. As the product design is becoming user-oriented, the usability of the product calls for the touch input function of the display panel which becomes an emphasis in the development of the display device industry.
As FIG. 1a shows, conventional Liquid Crystal Display (LCD) panel of with touch-input function includes a display panel 10 and a touch sensor 30. The touch panel 30 is disposed on the display surface 11 of the display panel 10. The images are displayed through the touch panel 30. The majority of touch panels includes resistive and capacitive touch panels.
As for the resistive touch panel 30, the operation principle includes using the voltage drop to locate the coordinates of the contact point. The touch panel 30 is composed of an upper layer and a lower layer and voltages are applied across two layers in two dimension. When the user physically points at the contact point, a conducting loop is created at the contact point. A voltage drop then occurs at the conducting loop which is then processed by the system. The system can then determine the location of the contact point. However the resistive touch panel 30 cannot accept multi-input simultaneously and also cannot process fingerprint recognition. Furthermore, a minimum applied pressure is required in order to create an effective conducting loop at the contact point, and thus the resistive touch panel 30 is subject to the limit of minimum applied force.
The operation principle of capacitive touch panel 30 is different to that of the resistive touch panel 30. As for the conventional capacitive touch panel shown in FIG. 1b, X direction electrodes 31 and Y direction electrodes 31 are respectively disposed on the upper and a lower layer. A difference in capacitance is created when the user physically points at the touch panel 30 using fingers or other objects. The system will be able to determine the contact point based on the difference in capacitance. As FIG. 1b shows, the electrodes 31 on the same row or column form continuous electrode strings. The electrode strings are arranged in accordance with X direction and Y direction of coordinate system. Excessive amount of electrodes 31 on the same row or the same column may result in excessive resistance or capacitance in the overall system. Furthermore, rows or columns of the electrode strings will be checked separately and thus it will be difficult to reduce the detect time and reaction time of the overall system.